As a conventional charged particle accelerator is known an FFAG (Fixed Field Alternating Gradient) accelerator in which magnetic field generated by a bending magnet is fixed and an equilibrium orbit is expanded to the outside of a round orbit while accelerating charged particles. (See non-patent document 1, for example).
Furthermore, a betatron is known as an accelerator in which an equilibrium orbit is not varied and acceleration is carried out along a fixed orbit. (See non-patent document 2, for example).
[Non-patent document 1]
“Development of a FFAG proton synchrotron” Proceedings of EPAC 2000, Vienna Austria 2000. pp 581-583, FIG. 1.
[Non-patent Document 2]
Accelerator Science (Parity Physics Course) issued on Sep. 20, 1993 by Maruzen Company, Chapter 4 BETATRON, pp 39-43, FIG. 4.1.
According to the FFAG accelerator disclosed in the non-patent document 1, a beam generated by an ion source is injected to the accelerator, and accelerated by electric field applied to an accelerating cavity while going along a substantially circular orbit under bending magnetic field of a bending magnet. During the acceleration, the bending magnetic field of the bending magnet is fixed, and the equilibrium orbit is shifted to the outside of the accelerator while the beam is accelerated.
The magnetic field strength of the bending magnet increases toward the outside thereof, however, the overall dimension of the apparatus is increased because the magnetic field of the bending magnet is fixed, so that it is difficult to miniaturize the apparatus and thus an application field is limited.
According to the betatron accelerator disclosed in the non-patent document 2, the equilibrium orbit is fixed during acceleration of charged particles, large-current acceleration is difficult because of a space charge effect caused by coulomb scattering and time-averaged beam power is weak, so that this accelerator is hardly applicable to industrial and medical fields.
The present invention has been implemented to solve the above problems, and has an object to provide a charged particle accelerator which is remarkably compact like a lap-top type of about 30 cmφ and large-current acceleration can be performed when electrons as charged particles are accelerated, thereby expanding applications to industrial and medical fields and other fields.
Furthermore, the present invention has an object to provide a compact accelerator even when protons, carbons or the like as charged particles are accelerated.